This R21 will explore the effects of HIV-1 exposure and opiate addiction and their interactions on the ability of the BBB to express and secrete cytokines. The blood-brain barrier (BBB) has emerged as a significant source of cytokines, prostaglandins, nitric oxide, and other potentially neurotoxic substances. Immune insults, including HIV-1, its glycoprotein coat (gp120), and Tat can induce the release of cytokines from the BBB and the brain endothelial cells (BEC) which comprise the BBB. Cytokines are believed to play a major role in neuroAIDS. The BBB is a unique source of cytokines in that HIV and its proteins would not have to enter the CNS to induce cytokine release. We have shown that HIV-1 or gp120 acts at the luminal (blood side) surface of BEC to induce the BBB to release the nitric oxide releasing cytokine endothelin-1 from its abluminal (brain side). Opiates modify the release of cytokines from various cell types and modify BBB function. We hypothesize that the HIV-1-induced release of cytokines by the BBB is enhanced in morphine addiction. We will test this hypothesis in two specific aims. In Specific Aim 1, we will determine which cytokines are upregulated after in vitro exposure to HIV-1, gp120, and Tat in BBB endothelial cells derived from control and morphine addicted mice. In Specific Aim 2, we will determine whether cytokines shown in Specific Aim 1 to be upregulated are overexpressed after in vivo exposure to HIV-1, gp120, or Tat in control and morphine addicted mice. We will do this by measuring mRNA cytokine levels in BEC and cytokine levels in BEC supernatant (Specific Aim 1) serum, brain homogenate, and cerebrospinal fluid (Specific Aim 2). These experiments will for the first time systematically examine which cytokines can be secreted by the BBB, will determine the effects of HIV-1, gp120, Tat, and morphine addiction on expression and release of cytokines by the BBB, and will examine the interaction of morphine addiction with HIV-1, gp120, and Tat on cytokine expression and release.